The NJR Implant Scrutiny Committee reports Level 1 outlier implants to the MHRA. There are currently 12 hip stems, 11 hip acetabular (cup) components and 33 hip stem / cup combinations reported. A total of 18 knee brands are currently reported. Knee implants with and without patella resurfacing are now included in implant outlier analysis.

An implant is considered to be a Level 1 outlier when its Prosthesis Time Incident Rate (PTIR) is more than twice the PTIR of the group, allowing for confidence intervals. These are shown as the number of revisions per 100 prosthesis-years. As of March 2015, we have started to identify the best performing implants, these would have a PTIR less than half that of their group, allowing for confidence intervals. To date no implants have reached that level.

Components and constructs previously reported to MHRA, but no longer at Level 1 using the PTIR method are identified.

Hip implant performance

Knee implant performance

Implants may be subjected to closer scrutiny under certain conditions, such as when reports are received from surgeons concerned about the performance of certain variants, or when a device seems to have a very specific mode of failure. Kaplan-Meier analysis of revision rate is performed, using the average for all knees recorded in the registry as the “expected” value, and if necessary, followed up with other statistical tests. If a variant is found to be significantly (P<0.001) outside the expected range, then this is also reported to the implant manufacturer and the MHRA.

Any surgeons who have specific concerns about the performance of joint replacement implants and/ or specific variants that would benefit from closer examination, can contact the NJR Implant Scrutiny Committee at